Extracellular lipids of Candida albicans biofilm induce lipid droplet formation and decreased response to a topoisomerase I inhibitor in dysplastic and neoplastic oral cells

Abstract Objective Some microorganisms, i.e., Candida albicans, have been associated with cancer onset and development, although whether the fungus promotes cancer or whether cancer facilitates the growth of C. albicans is unclear. In this context, microbial-derived molecules can modulate the growth and resistance of cancer cells. This study isolated extracellular lipids (ECL) from a 36-h Candida albicans biofilm incubated with oral dysplastic (DOK) and neoplastic (SCC 25) cells, which were further challenged with the topoisomerase I inhibitor camptothecin (CPT), a lipophilic anti-tumoral molecule. Methodology ECL were extracted from a 36-h Candida albicans biofilm with the methanol/chloroform precipitation method and identified with Nuclear Magnetic Resonance (1H-NMR). The MTT tetrazolium assay measured ECL cytotoxicity in DOK and SCC 25 cells, alamarBlue™ assessed cell metabolism, flow cytometry measured cell cycle, and confocal microscopy determined intracellular features. Results Three major classes of ECL of C. albicans biofilm were found: phosphatidylinositol (PI), phosphatidylcholine (PC), and phosphatidylglycerol (PG). The ECL of C. albicans biofilm had no cytotoxic effect on neither cell after 24 hours, with a tendency to disturb the SCC 25 cell cycle profile (without statistical significance). The ECL-induced intracellular lipid droplet (LD) formation on both cell lines after 72 hours. In this context, ECL enhanced cell metabolism, decreased the response to CPT, and modified intracellular drug distribution. Conclusion The ECL (PI, PC, and PG) of 36-h Candida albicans biofilm directly interacts with dysplastic and neoplastic oral cells, highlighting the relevance of better understanding C. albicans biofilm signaling in the microenvironment of tumor cells.

摘要 研究目的：部分微生物——即白色念珠菌（Candida albicans）——已被证实与癌症的发生及发展存在关联，但目前尚不清楚该真菌是促进癌症发生，还是癌症会促进白色念珠菌的增殖。在此背景下，微生物来源的分子可调控癌细胞的生长与耐药性。本研究从与口腔发育异常细胞（DOK）及肿瘤细胞（SCC 25）共培养36小时的白色念珠菌生物被膜中分离得到细胞外脂质（extracellular lipids, ECL），并使用拓扑异构酶I抑制剂喜树碱（camptothecin, CPT）——一种亲脂性抗肿瘤分子——对上述细胞进行刺激处理。
研究方法：本研究采用甲醇/氯仿沉淀法从白色念珠菌生物被膜中提取ECL，并通过核磁共振波谱（¹H-NMR）对其进行鉴定。采用MTT四唑盐实验检测ECL对DOK细胞与SCC 25细胞的细胞毒性，使用alamarBlue™试剂盒评估细胞代谢水平，通过流式细胞术检测细胞周期，并利用共聚焦显微镜分析细胞内特征。
研究结果：本研究在白色念珠菌生物被膜的ECL中鉴定出三大类脂质：磷脂酰肌醇（phosphatidylinositol, PI）、磷脂酰胆碱（phosphatidylcholine, PC）以及磷脂酰甘油（phosphatidylglycerol, PG）。ECL在24小时内未对两种细胞产生细胞毒性，但存在扰乱SCC 25细胞周期分布的趋势（无统计学显著性）。培养72小时后，ECL可诱导两种细胞系内形成细胞内脂滴（lipid droplet, LD）。在此背景下，ECL可增强细胞代谢水平，降低细胞对CPT的响应，并改变细胞内药物分布。
研究结论：与口腔发育异常细胞及肿瘤细胞共培养36小时的白色念珠菌生物被膜所产生的ECL（PI、PC及PG）可直接作用于上述口腔细胞，这凸显了深入解析肿瘤微环境中白色念珠菌生物被膜信号通路的重要性。